Broadband Light Source Based on Four-Color Self-Assembled InAs Quantum Dot Ensembles Monolithically Grown in Selective Areas (original) (raw)
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Journal of Applied Physics, 2016
We report a broadband-gain superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) for application in a high-resolution optical coherence tomography (OCT) light source. Four InAs QD layers, with sequentially shifted emission wavelengths achieved by varying the thickness of the In 0.2 Ga 0.8 As strain-reducing capping layers, were embedded in a conventional p-n heterojunction comprising GaAs and AlGaAs layers. A ridge-type waveguide with segmented contacts was formed on the grown wafer, and an as-cleaved 4-mm-long chip (QD-SLD) was prepared. The segmented contacts were effective in applying a high injection current density to the QDs and obtaining emission from excited states of the QDs, resulting in an extension of the bandwidth of the electroluminescence spectrum. In addition, gain spectra deduced with the segmented contacts indicated a broadband smooth positive gain region spanning 160 nm. Furthermore, OCT imaging with the fabricated QD-SLD was performed, and OCT images with an axial resolution of $4 lm in air were obtained. These results demonstrate the effectiveness of the QD-SLD with segmented contacts as a highresolution OCT light source. V
Materials, 2016
We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode's active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to 2 nm, allowing a tunable emission band over 160 nm. The emission wavelength blueshift has been ensured by reducing both dots' height and composition. A structure containing four vertically stacked height-engineered QDs have been fabricated, showing a room temperature broad emission band centered at 1.1 µm. The buried QD layers remain insensitive to the In-flush process of the subsequent layers, testifying the reliability of the process for broadband light sources required for high axial resolution OCT imaging.
Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering
IEEE Journal of Selected Topics in Quantum Electronics, 2000
We present a 18 mW fiber-coupled single-mode superluminescent diode with 85 nm bandwidth for application in optical coherence tomography (OCT). First, we describe the effect of quantum dot (QD) growth temperature on optical spectrum and gain, highlighting the need for the optimization of epitaxy for broadband applications. Then, by incorporating this improved material into a multicontact device, we show how bandwidth and power can be controlled. We then go on to show how the spectral shape influences the autocorrelation function, which exhibits a coherence length of <11 µm, and relative noise is found to be 10 dB lower than that of a thermal source. Finally, we apply the optimum device to OCT of in vivo skin and show the improvement that can be made with higher power, wider bandwidth, and lower noise, respectively.
IEEE Journal of Selected Topics in Quantum Electronics, 2007
Quantum dot (QD) superluminescent diodes (SLDs) exhibiting 8 mW and 95 nm full-width at half-maximum centered at 1270 nm are demonstrated with a flat-topped spectral profile. This is achieved using 3 × 2 dots in compositionally modulated wells technique. Furthermore, techniques for realization of high-power SLDs are also demonstrated. A continuous-wave output power of 42 mW is achieved for narrowband devices centered at 1250 nm.
Multi-section quantum dot superluminescent diodes for spectral shape engineering
IET Optoelectronics, 2009
The design and operating parameters of a novel multi-contact quantum dot superluminescent diode incorporating a number of features which inhibit lasing are described and compared with that of a single-contact device. Such devices allow the independent tuning of emission power and spectral shape; hence the penetration depth and resolution in optical coherence tomography are decoupled. The emission spectrum of a device utilising chirped quantum dots is shown to be tuned to produce a broadband single Gaussian emission, centred at the required wavelength of 1050 nm, at higher output powers than a singlecontact device.
InGaAs/GaAs Quantum-Dot Superluminescent Diode for Optical Sensor and Imaging
IEEE Sensors Journal, 2007
We report on the design and fabrication of a novel wideband superluminescent diode (SLD) based on InGaAs/GaAs quantum-dot structure. In this device, we monolithically integrate a photon absorber section to suppress lasing action and optical feedback oscillation. The fabricated SLDs produce a close-to-Gaussian shaped spectrum centered at 1210 nm with a bandwidth of 135 nm. Spectral ripple as low as 0.3 dB has been measured.
Integrated tunable quantum dot laser for optical coherence tomography in the 1.7µm wavelength region
Journal of The Optical Society of America A-optics Image Science and Vision, 2011
We have designed and fabricated a monolithically integrated continuously tunable laser source for frequency domain optical coherence tomography (FD-OCT) in the 1.6 to 1.8μm wavelength region. The InP-based laser consists of two 8mm long quantum dot (QD) semiconductor optical amplifiers and two electro-optically (EO) tunable filters in a 43.5 mm long ring laser cavity. An 8mm long output amplifier is used to boost the output signal.
Japanese Journal of …, 2010
Cleaved edge overgrowth and selective area epitaxy were combined for the synthesis of InAs quantum dot (QD) arrays with lateral sizes from 20 to 40 nm. The optical properties were locally assessed by confocal photoluminescence spectroscopy experiments at liquid helium temperature. The emission lines redshift as the lateral size of the QDs is increased. In agreement with a narrow size distribution, significantly narrow emission lines are observed for measurements in QD ensembles. Excitation power dependent luminescence measurements were realized on QD ensembles. A shell filling behavior was observed. The same measurements realized on single QDs led to the observation of multiple excitonic effects. Polarization dependent luminescence measurements indicate the existence of in-plane optical anisotropy, which strictly follows in-plane morphological anisotropy of the QDs. These results are encouraging for the use of quantum dot arrays in quantum information science and technology, as well as for new device concepts.